1. Field of the Invention
The present invention relates to a syringe, and more particularly to a safety syringe that can retract the used needle.
2. Description of Related Art
A conventional syringe has a hollow barrel, a plunger and a needle hub. Due to contagious diseases, the needle of the syringe and even the hollow barrel and the plunger, should not be used again and should be discarded immediately after use. Also, to keep nurses, doctors or health workers who deal with discarded syringes from getting injured or infected by used needles, a safety syringe is needed. In particular, manufacturers have focused on syringes with retractable needles so that once the syringe has been used, the contaminated needle is entirely housed within the barrel whereby the chance of infection through accidental pricking is eliminated.
A conventional safety syringe disclosed in Taiwan Pat. No. 356013 comprises a hollow barrel, a plunger and a needle hub. The plunger has a connector formed on one end of the plunger to connect with the needle hub. The connector has a protrusion. The needle hub comprises a recess and an annular rib. The recess has a distal closed end and a proximal open end. The annular rib extends radially inward from the proximal open end of the recess. The protrusion of the connector can be clipped by the annular rib of the needle hub to connect the plunger and the needle hub together. When the plunger is pushed to the needle hub, the plunger with the connector becomes connected with the needle hub to retract the needle hub into the hollow barrel.
However, the conventional safety syringe often retracts the needle hub before use. Since the medical personnel will customarily push the plunger toward the needle hub to eject air before a medical solution is drawn into the safety syringe, the medical personnel often forgets that with the safety syringe the plunger can not be pushed to the front most end at this time. Thus, the plunger will connect with the needle hub and the needle hub will retract back in the hollow barrel. In this situation, the safety syringe can no longer be used and the safety syringe is wasted.